我正在使用Qt Quick，我想为我的应用程序创建一个标题栏。所以我继承了QQuickPaintedItem，在上面画了一点，并想把它用作Window的标题栏。我使用的是Qt 5.7。这成功了，但只是在一定程度上;我将在代码后解释更多。
我是这样做的：

main.cpp

#include <QGuiApplication>
#include <QQmlApplicationEngine>

#include "mycustomtitlebar.h"

int main(int argc, char *argv[])
{
    QGuiApplication app(argc, argv);

    qmlRegisterType<MyCustomTitleBar>("my.custom.lib", 1, 0, "MyCustomTitleBar");

    QQmlApplicationEngine engine;
    engine.load(QUrl(QStringLiteral("qrc:/main.qml")));

    return app.exec();
}

字符串

main.qml

import QtQuick 2.7
import QtQuick.Window 2.2
import my.custom.lib 1.0

Window {
    id: wnd
    visible: true
    width: 640
    height: 480
    title: qsTr("Hello World")

    MyCustomTitleBar {
        id: titleBar
        anchors.top: parent.top
        anchors.left: parent.left
        anchors.right: parent.right
        height: 100
        hostWidget: wnd
    }

    Rectangle {
        color: "beige"
        anchors.top: titleBar.bottom
        anchors.left: parent.left
        anchors.right: parent.right
        anchors.bottom: parent.bottom
    }
}

型

mycustomtitlebar.h

#ifndef MYCUSTOMTITLEBAR_H
#define MYCUSTOMTITLEBAR_H

#include <QQuickPaintedItem>
#include <QPoint>

class MyCustomTitleBar : public QQuickPaintedItem
{
    Q_OBJECT

    Q_PROPERTY(QWindow *hostWidget READ hostWidget WRITE setHostWidget)

public:
    MyCustomTitleBar(QQuickItem *parent = 0);

protected:
    virtual void paint(QPainter *pPainter) Q_DECL_OVERRIDE;
    virtual void mousePressEvent(QMouseEvent *pEvent) Q_DECL_OVERRIDE;
    virtual void mouseMoveEvent(QMouseEvent *pEvent) Q_DECL_OVERRIDE;
    virtual void mouseReleaseEvent(QMouseEvent *pEvent) Q_DECL_OVERRIDE;

private:
    QWindow *hostWidget() const;
    void setHostWidget(QWindow *pHostWidget);

private:
    QWindow *m_pHostWidget;
    QPoint m_initialMousePosition;
    bool m_leftMouseButtonPressed;
};

#endif // MYCUSTOMTITLEBAR_H

型

mycustomtitlebar.cpp

#include "mycustomtitlebar.h"

#include <QPainter>
#include <QDragMoveEvent>
#include <QWindow>

MyCustomTitleBar::MyCustomTitleBar(QQuickItem *parent)
    : QQuickPaintedItem(parent),
      m_leftMouseButtonPressed(false),
      m_pHostWidget(Q_NULLPTR)
{
    setAcceptedMouseButtons(Qt::AllButtons);
}

void MyCustomTitleBar::paint(QPainter *pPainter)
{
    // Dummy drawing...
    const QRect myRect(10, 10, width() - 20, height() - 20);
    qDebug() << myRect;
    pPainter->drawRect(myRect);
}

void MyCustomTitleBar::mousePressEvent(QMouseEvent *pEvent)
{
    m_leftMouseButtonPressed = true;
    m_initialMousePosition = pEvent->pos();
}

void MyCustomTitleBar::mouseMoveEvent(QMouseEvent *pEvent)
{
    if (m_leftMouseButtonPressed) {
        if (!m_pHostWidget) {
            qDebug() << Q_FUNC_INFO << "Host widget not set. Please set host widget";
            return;
        }

        const QPoint newMousePosition = pEvent->pos() - m_initialMousePosition + m_pHostWidget->position();
        m_pHostWidget->setPosition(newMousePosition);
    }

    QQuickPaintedItem::mouseMoveEvent(pEvent);
}

void MyCustomTitleBar::mouseReleaseEvent(QMouseEvent *pEvent)
{
    m_leftMouseButtonPressed = false;
}

QWindow *MyCustomTitleBar::hostWidget() const
{
    return m_pHostWidget;
}

void MyCustomTitleBar::setHostWidget(QWindow *pHostWidget)
{
    m_pHostWidget = pHostWidget;
}

型
现在这段代码工作得很好，我运行应用程序，我可以点击标题栏并拖动，整个窗口移动到我想要的地方。

但是，这里有一个问题：如果我把hostWidget: wnd改成hostWidget: parent，它就不工作了.有人能解释一下为什么吗？因为wnd毕竟是parent.

P.S.
我也从Qt Creator得到了这个非常奇怪的错误通知，但代码编译并运行良好：x1c 0d1x
为什麽？